NAME

     rinetd — internet “redirection server”

SYNOPSIS

     /usr/sbin/rinetd

VERSION

     Version 0.62, 04/14/2003.

DESCRIPTION

     rinetd redirects TCP connections from one IP address and port to another. rinetd is a single-process server
     which handles any number of connections to the address/port pairs specified in the file /etc/rinetd.conf.
     Since rinetd runs as a single process using nonblocking I/O, it is able to redirect a large number of
     connections without a severe impact on the machine. This makes it practical to run TCP services on machines
     inside an IP masquerading firewall. rinetd does not redirect FTP, because FTP requires more than one
     socket.

     rinetd is typically launched at boot time, using the following syntax:

     /usr/sbin/rinetd

     The configuration file is found in the file /etc/rinetd.conf, unless another file is specified using the -c
     command line option.

FORWARDING RULES

     Most entries in the configuration file are forwarding rules. The format of a forwarding rule is as follows:

     bindaddress bindport connectaddress connectport

     For example:

     206.125.69.81 80 10.1.1.2 80

     Would redirect all connections to port 80 of the "real" IP address 206.125.69.81, which could be a virtual
     interface, through rinetd to port 80 of the address 10.1.1.2, which would typically be a machine on the
     inside of a firewall which has no direct routing to the outside world.

     Although responding on individual interfaces rather than on all interfaces is one of rinetd's primary
     features, sometimes it is preferable to respond on all IP addresses that belong to the server.  In this
     situation, the special IP address 0.0.0.0 can be used. For example:

     0.0.0.0 23 10.1.1.2 23

     Would redirect all connections to port 23, for all IP addresses assigned to the server. This is the default
     behavior for most other programs.

     Service names can be specified instead of port numbers. On most systems, service names are defined in the
     file /etc/services.

     Both IP addresses and hostnames are accepted for bindaddress and connectaddress.

ALLOW AND DENY RULES

     Configuration files can also contain allow and deny rules.

     Allow rules which appear before the first forwarding rule are applied globally: if at least one global
     allow rule exists, and the address of a new connection does not satisfy at least one of the global allow
     rules, that connection is immediately rejected, regardless of any other rules.

     Allow rules which appear after a specific forwarding rule apply to that forwarding rule only. If at least
     one allow rule exists for a particular forwarding rule, and the address of a new connection does not
     satisfy at least one of the allow rules for that forwarding rule, that connection is immediately rejected,
     regardless of any other rules.

     Deny rules which appear before the first forwarding rule are applied globally: if the address of a new
     connection satisfies any of the global deny rules, that connection is immediately rejected, regardless of
     any other rules.

     Deny rules which appear after a specific forwarding rule apply to that forwarding rule only. If the address
     of a new connection satisfies any of the deny rules for that forwarding rule, that connection is
     immediately rejected, regardless of any other rules.

     The format of an allow rule is as follows:

     allow pattern

     Patterns can contain the following characters: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, . (period), ?, and *. The ?
     wildcard matches any one character. The * wildcard matches any number of characters, including zero.

     For example:

     allow 206.125.69.*

     This allow rule matches all IP addresses in the 206.125.69 class C domain.

     Host names are NOT permitted in allow and deny rules. The performance cost of looking up IP addresses to
     find their corresponding names is prohibitive. Since rinetd is a single process server, all other
     connections would be forced to pause during the address lookup.

LOGGING

     rinetd is able to produce a log file in either of two formats: tab-delimited and web server-style "common
     log format."

     By default, rinetd does not produce a log file. To activate logging, add the following line to the
     configuration file:

     logfile log-file-location

     Example: logfile /var/log/rinetd.log

     By default, rinetd logs in a simple tab-delimited format containing the following information:

     Date and time

     Client address

     Listening host

     Listening port

     Forwarded-to host

     Forwarded-to port

     Bytes received from client

     Bytes sent to client

     Result message

     To activate web server-style "common log format" logging, add the following line to the configuration file:

     logcommon

COMMAND LINE OPTIONS

     The -c command line option is used to specify an alternate configuration file.

     The -f command line option is used to run rinetd in the foreground, without forking to the background.

     The -h command line option produces a short help message.

     The -v command line option displays the version number.

REINITIALIZING RINETD

     The kill -1 signal (SIGHUP) can be used to cause rinetd to reload its configuration file without
     interrupting existing connections.  Under Linux™ the process id is saved in the file /var/run/rinetd.pid to
     facilitate the kill -HUP. An alternate filename can be provided by using the <code>pidlogfile</code>
     configuration file option.

LIMITATIONS

     rinetd redirects TCP connections only. There is no support for UDP. rinetd only redirects protocols which
     use a single TCP socket. This rules out FTP.

BUGS

     The server redirected to is not able to identify the host the client really came from. This cannot be
     corrected; however, the log produced by rinetd provides a way to obtain this information. Under Unix,
     Sockets would theoretically lose data when closed with SO_LINGER turned off, but in Linux this is not the
     case (kernel source comments support this belief on my part). On non-Linux Unix platforms, alternate code
     which uses a different trick to work around blocking close() is provided, but this code is untested. The
     logging is inadequate.  The duration of each connection should be logged.

LICENSE

     Copyright (c) 1997, 1998, 1999, Thomas Boutell and Boutell.Com, Inc.  This software is released for free
     use under the terms of the GNU Public License, version 2 or higher. NO WARRANTY IS EXPRESSED OR IMPLIED.
     USE THIS SOFTWARE AT YOUR OWN RISK.

CONTACT INFORMATION

     See http://www.boutell.com/rinetd/ for the latest release.  Thomas Boutell can be reached by email:
     boutell@boutell.com

THANKS

     Thanks are due to Bill Davidsen, Libor Pechachek, Sascha Ziemann, the Apache Group, and many others who
     have contributed advice and/or source code to this and other free software projects.